Storage Wrap Material

ABSTRACT

The present invention relates to sheet-like materials suitable for use in the containment and protection of various items, as well as the preservation of perishable materials such as food items. More particularly, the present invention provides an improved storage wrap material comprising a sheet of material having a first side and a second side. The first side comprises an active side exhibiting an adhesion peel force after activation by a user which is greater than an adhesion peel force exhibited prior to activation by a user. The storage wrap material may be activated by different approaches, but in a preferred embodiment the active side is activatible by an externally applied force exerted upon the sheet of material. The force may be an externally applied compressive force exerted in a direction substantially normal to the sheet of material. In accordance with the present invention, the storage wrap material is selectively activatible by a user in discrete regions to provide adhesive properties where and when desired. The use of an adhesive or adhesive-like substance on the surface of the material provides an adhesion peel force after activation which is sufficient to form a barrier seal against a target surface at least as great as those of the material and the target surface such that perishable items, such as food items, may be effectively preserved. The storage wrap materials of the present invention may be utilized to enclose and protect a wide variety of items by various methods of application, including direct application to the desired item, enclosure of the desired item and securement to itself, and/or in combination with a semi-enclosed container.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 11/490,699,filed Jul. 21, 2006; which is a continuation of application Ser. No.09/715,586, filed Nov. 20, 2000; which is a continuation of applicationSer. No. 08/745,340, filed Nov. 8, 1996; which is a continuation-in-partof application Ser. No. 08/584,638, filed Jan. 10, 1996.

FIELD OF THE INVENTION

The present invention relates to sheet-like materials suitable for usein the containment and protection of various items, as well as thepreservation of perishable materials such as food items. The presentinvention further relates to such materials which are suitable fordirect contact with such items as a unitary package as well as for usein forming a closure for a semi-enclosed container.

BACKGROUND OF THE INVENTION

Sheet-like materials for use in the containment and protection ofvarious items, as well as the preservation of perishable materials suchas food items, are well known in the art. Such materials can be utilizedto wrap items individually and/or can be utilized to form a closure fora semi-enclosed container.

One class of such materials in common use today comprises those ofpolymeric composition formed into a thin, conformable web commonlysupplied in rolled form. Common examples of such materials are polyvinylchloride (PVC), polyvinylidene chloride (PVDC), and polyethylene (PE)sheet materials. These materials exhibit a clinging character on atleast one surface due to the properties of the polymeric materials theyare formed from and/or additives such as plasticizers, tackifiers, etc.,such that they may be folded or wrapped around an item such that theycling to the item and/or to themselves. The clinging character of suchmaterials also permits their use in combination with semi-enclosedrigid, semi-rigid, or flexible containers to provide a fully enclosedcontainer structure. The barrier properties of many such materials,particularly their oxygen, moisture/moisture vapor, and odor barrierproperties, provide the desired preservation characteristics forperishable items such as food items and/or items which oxidize orotherwise degrade more rapidly with continued exposure to environmentalconditions.

While these materials have achieved a certain level of acceptance, wherethe material is supplied in the form of a continuous roll in adispensing carton or apparatus, difficulty is often encountered locatingand isolating the current end portion of the rolled web in order tostart the dispensing operation. In order to address this issue, a numberof methods of identifying and/or isolating the current end of the rolledweb have been developed (tabs, colors, end-grasping dispenser features,etc.) which have achieved varying levels of success. Irregardless of theissue of handling the end of the rolled web, the tendency of thematerial to cling to itself also increases the dispensing force requiredto unroll the web and tangentially separate the dispensed portion and,if excessive, can lead to a phenomenon known as “roll blocking” whereinthe dispensing force to unroll becomes excessive. Roll blocking can alsocause excessive dispensing forces which can lead to longitudinal tearingof the web in the roll direction, leading the user to dispense anarrower, unevenly-torn portion of the rolled web. In addition, usersfrequently encounter situations wherein the material clings to itselfprematurely (i.e., before contacting the desired bonding surface), thusnecessitating either the manual disengagement of the clinging portion(s)and/or discarding of the material in favor of a new portion.

Another difficulty which may be encountered is the failure of thematerial to adhere to itself and/or the desired target surfacesufficiently to form an airtight seal either from the outset or after aperiod of handling of the container or wrapped item. If such materialscannot form a seal with barrier properties at least as great as those ofthe material itself, the full potential of such materials in use as astorage wrap cannot be realized as the seal becomes the weakest link interms of containerization. Accordingly, some users employ additionalsecurement features such as rubber bands, tapes, etc. Wrinkles in thematerial where it clings to itself or a target surface can leave smallchannels in the region between the material and the opposing surface,thereby causing a failure to achieve the desired seal quality forpreservation of perishable items. Some users attempt to address sealquality shortcomings by double- or triple-wrapping the desired item toform a tortuous labyrinth seal path of increased length.

Also, because the materials “cling” to themselves and other surfaces,i.e., exhibit an attraction or affinity for the material rather than anadhesive bond, their affinity for a complementary surface is highlydependent upon material characteristics such as chemical composition,electrical conductivity, surface energy, surface finish, etc. Therefore,such materials leave room for improvement both in ease of use as well asability to form an adequate seal for preservation of perishable items.In many instances, the plasticizers, tackifiers, and other clingadditives utilized to provide the cling properties of such materials mayalso introduce undesirable attributes such as odor to the finished weband/or may introduce environmental concerns.

Another class of materials in common use today comprises thin,conformable webs of various compositions commonly supplied in individualsheet or rolled form. Common examples of such materials include aluminumfoil, coated (waxed, etc.) paper, etc. These materials exhibit noadhesive or cling character on either surface, instead relying upon thedead-fold characteristics of the materials they are formed from suchthat they may be folded or wrapped around an item and retain theirfolded or wrapped shape. The ability of these materials to maintaintheir folded or creased shape also permits their use in combination withsemi-enclosed rigid, semi-rigid, or flexible containers to provide afully enclosed container structure. The barrier properties of many suchmaterials, particularly their oxygen, moisture/moisture vapor, and odorbarrier properties, provide the desired preservation characteristics forperishable items such as food items and/or items which oxidize orotherwise degrade more rapidly with continued exposure to environmentalconditions.

While these materials have achieved a certain level of acceptance, usersfrequently encounter situations wherein the material fails to remainsufficiently folded and engaged with itself and/or a semi-enclosedcontainer to adequately enclose and preserve the item (i.e., the foldstend to unfold with time or mechanical disturbance), thus necessitatingeither refolding and external securement of the folded portion(s) and/ordiscarding of the material in favor of a new portion andre-accomplishing the wrapping process. In some instances, such materialsmay also be constructed of very thin materials in order to achieve thedesired degree of conformability. This may result in the material havinginsufficient tensile properties to dispense from a roll withoutlongitudinal tearing of the web in the roll direction, leading the userto dispense a narrower, unevenly-torn portion of the rolled web.

Another difficulty which may be encountered is the failure of thematerial to form an adequate seal where folded either from the outset orafter a period of handling of the container or wrapped item. If suchmaterials cannot form a seal with barrier properties at least as greatas those of the material itself, the full potential of such materials inuse as a storage wrap cannot be realized as the seal becomes the weakestlink in terms of containerization. Accordingly, some users undertake toemploy additional securement features such as rubber bands, tapes, etc.Wrinkles in the material where it meets itself or a target surface canleave small channels in the region between the material and the opposingsurface, thereby causing a failure to achieve the desired seal qualityfor preservation of perishable items. Some users attempt to address sealquality shortcomings by double- or triple-wrapping the desired item toform a tortuous labyrinth seal path of increased length.

The effective fold radius of these materials is also a factor indetermining their suitability for forming an effective seal, as the foldradius of some materials (paper based, etc.) is determined by suchmaterial properties as fiber length. A fold radius which is too largewill generally render such a material unsuitable for forming aneffective seal. In addition, due to the fact that most such dead-foldtype materials are opaque, the condition and/or type of items containedin such a packaging system are also obscured from view, necessitatingun-wrapping and re-wrapping the items to permit inspection.

Such materials, due to their lack of any adhesive properties, are alsodifficult to effectively employ in the preservation of perishable itemsin combination with a semi-enclosed container where the containerprovides no physical or mechanical engagement features (such as aconventional bowl) around which to fold the material to effect amechanical labyrinth-type seal between the material and the container.Therefore, such materials leave room for improvement both in ease of useas well as ability to form an adequate seal for preservation ofperishable items.

Accordingly, it would be desirable to provide an improved storage wrapmaterial which exhibits convenient, efficient dispensing by a user byhaving a readily located end portion and a comparatively low unrollingforce.

It would also be desirable to provide such a material which is easilyhandled and manipulated by a user during the enclosure process yet formsan adequate seal with a wide variety of materials and surfaces toeffectively preserve perishable items.

It would also be desirable to provide such a material which is capableof being utilized in various modes of item containment and preservationas desired by a user, such as independent use and/or use in combinationwith a semi-enclosed container, in efficient fashion by substantiallyreducing if not eliminating the need for double-wrapping and/oradditional securement features.

It would further be desirable to provide such materials which arecapable of being readily manufactured, stored, and re-used as desirablefor both economic and environmental efficiency.

SUMMARY OF THE INVENTION

The present invention provides an improved storage wrap materialcomprising a sheet of material having a first side and a second side.The first side comprises an active side exhibiting an adhesion peelforce after activation by a user which is greater than an adhesion peelforce exhibited prior to activation by a user.

The storage wrap material may be activated by different approaches, butin a preferred embodiment the active side is activatible by anexternally applied force exerted upon the sheet of material. The forcemay be an externally applied compressive force exerted in a directionsubstantially normal to the sheet of material or may be an externallyapplied tensile force exerted in a direction substantially parallel tothe sheet of material.

The active side of the storage wrap material preferably exhibits anadhesion peel force of at least about 1 ounce per linear inch, morepreferably between about 1 and about 2.5 ounces per linear inch, afteractivation by a user. In accordance with the present invention, thestorage wrap material is selectively activatible by a user in discreteregions to provide adhesive properties where and when desired. The useof an adhesive or adhesive-like substance on the surface of the materialprovides an adhesion peel force after activation which is sufficient toform a barrier seal against a target surface at least as great as thoseof the material and the target surface such that perishable items, suchas food items, may be effectively preserved.

The storage wrap materials of the present invention may be utilized toenclose and protect a wide variety of items by various methods ofapplication, including direct application to the desired item, enclosureof the desired item and securement to itself, and/or in combination witha semi-enclosed container.

Such storage wrap materials of the present invention may beadvantageously employed in a container system comprising, incombination, the storage wrap material and a semi-enclosed containerwith at least one opening surrounded by a peripheral edge. The storagewrap material is adhered to the peripheral edge over the openingfollowing activation by a user to convert the semi-enclosed container toa closed container.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the present invention, it is believed that thepresent invention will be better understood from the followingdescription in conjunction with the accompanying Drawing Figures, inwhich like reference numerals identify like elements, and wherein:

FIG. 1 is a perspective view of the storage wrap material of the presentinvention provided in roll form;

FIG. 2 is a plan view of a preferred embodiment of a three-dimensional,nesting-resistant sheet material suitable for use as a storage wrapmaterial in accordance with the present invention;

FIG. 3 is a partial elevational sectional view of the sheet material ofFIG. 2, wherein a substance is included within the three-dimensionalstructure of the web;

FIG. 4 is a plan view of a three-dimensional forming structure suitablefor forming a three-dimensional, nesting resistant sheet material suchas that of FIG. 3;

FIG. 5 is a partial elevational sectional view of the three-dimensionalforming structure of FIG. 4;

FIG. 6 is a schematic illustration of a representative apparatussuitable for forming a storage wrap material in accordance with thepresent invention;

FIG. 7 is a perspective view of the storage wrap material of the presentinvention being formed into a unitary package around an item to bestored by bonding the material to itself around the item;

FIG. 8 is a perspective view of the storage wrap material of the presentinvention being utilized in combination with a semi-enclosed containerto form a closed container; and

FIG. 9 is a perspective view of the storage wrap material of the presentinvention being formed into a unitary package around an item to bestored by bonding overlying portions of the material to itself over theitem.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a preferred embodiment of a storage wrap material 10according to the present invention. As shown in FIG. 1, storage wrapmaterial 10 is preferably provided in the form of a web of flexiblematerial which can be wound upon a core to form a roll 20 which issuitable for use in a dispenser or holder such as carton 30. If desired,perforations may be provided to facilitate dispensing of pre-measureddimensions of the material in the event that the dispenser, holder, orcontainer does not include a suitable severing apparatus. Manualsevering with sharp implements such as knives and scissors may also beaccomplished in order to utilize the material in continuousnon-perforated form. In alternative storage and dispensingconfigurations, the storage wrap material may be provided in the form ofdiscrete, pre-measured sheets of uniform or non-uniform dimensions whichmay be stacked upon one another in any desired sequence and/ororientation and dispensed from a carton, bag, or any other suitabledispensing apparatus. In another alternative storage and dispensingconfiguration, the storage wrap material may be provided in the form ofa continuous web which is Z-folded or pleated and placed in a dispensingcarton.

In accordance with the present invention, storage wrap material 10exhibits minimal, and preferably no, adhesive or cling properties untilactivated by a user. This characteristic permits storage wrap 10 to bestored and dispensed in any desired mode without encountering thedifficulties of premature clinging or adhering to itself, and withoutthe need for separate release sheets, liners, spacers, or the like. Atthe same time, when activated at the desired location and at the desiredtime, the storage wrap material exhibits sufficient adhesive propertiesto form a bond to most common materials which is sufficiently strong soas to survive handling without failure. The bond between the storagewrap material and a target surface is also sufficient to provide abarrier seal against transmission of oxygen, moisture/moisture vapor,odor, etc. such that perishable items may be satisfactorily enclosed andpreserved to the extent of the barrier properties of the materialitself.

Although storage wrap material may be provided with two active sides orsurfaces, if desired for particular applications, in accordance with thepresent invention it is presently preferred to provide storage wrapmaterial with only one active side and one inactive or inert side.

The active side of the storage wrap material may be selectivelyactivated by a user to provide activated regions where desired toprovide selective adhesion of the material to a target surface. Thetarget surface may comprise a separate surface or material, such as acontainer or an item or items to be wrapped, or may comprise anotherportion of the storage wrap material itself. Selective activationresults in the generation of only so much active area with adhesiveproperties as is needed, i.e., all remaining portions of the storagewrap material remain inactive or inert. The storage wrap material istherefore capable of forming discrete inactive and active regions on thesame side of the material in addition to the ability to have an activeside and an inactive side.

Various means of activation are envisioned as being within the scope ofthe present invention, such as compression, extension, thermalactivation, etc. However, in terms of providing the user with thedesired degree of control over the activation process the compressionactivation method is presently preferred.

Regardless of the manner of activation, storage wrap materials of thepresent invention will exhibit an adhesive, adherent, or tackingcharacter as opposed to merely a clinging or affinity character.Accordingly, such storage wrap materials will form a bond or seal whenin contact with itself or another target surface as opposed to merelybeing attracted to such surface. While a number of approaches such asthe use of selectively adherent materials may be utilized to provide thedesired adhesive properties, a presently preferred approach is toutilize a pressure-sensitive adhesive. When designing storage wrapmaterials in accordance with the present invention, it may be desirableto tailor the particular choice of adhesive agent so as to provideeither a permanent bond or a releasable bond as desired for a particularapplication. Where a permanent bond is desired, opening of the wrap orenclosed container for access to the item(s) therein requiresdestruction of the storage wrap and/or the container. Releasable bonds,on the other hand, provide access to the wrapped item(s) by permittingseparation of the wrap from itself or the container at the bond sitewithout destruction. Moreover, depending upon the activation mechanismemployed in the design of the storage wrap material, the releasable bondmay additionally be refastenable if sufficient adhesive characterremains after the initial activation/bonding/release cycle.

Several physical characteristics or properties are believed to beimportant in the design and construction of a suitable storage wrapmaterial in accordance with the present invention.

In order to accommodate a wide range of items to be wrapped/packaged interms of shape and size, as well as a wide range of container shapeswhen utilized in combination with a semi-enclosed container, the storagewrap material is preferably sufficiently flexible to conform readily toany desired surface. At the same time, the memory or resiliency of thematerial must be sufficiently small that it does not exert unduerestorative forces which would tend to cause the material to breakcontact with the container/item/target surface and thus becomeprematurely unsecured or unsealed over time. While design of the storagewrap material for the intended application will require a balancing ofthe various physical properties, as a general proposition it ispresently preferred for a wide variety of applications to select amaterial having greater plasticity than elasticity.

Another property which has been found to be important in designingstorage wrap materials in accordance with the present invention is thedegree of adhesion that they exhibit after activation by a user. Moreparticularly, the storage wrap materials of the present inventionexhibit an adhesion sufficient to survive the likely degree of handlingthe wrapped item or enclosed container is likely to encounter in usewhile maintaining the desired level of sealing engagement with the item,with itself, or with the accompanying semi-enclosed container such thatpreservation of perishable items is ensured.

One way to measure or quantify this adhesion property is in terms of anadhesion peel force value which is preferably measured by PressureSensitive Tape Council Method PSTC-1. A 12 inch (30.5 cm) long by 1 inch(2.5 cm) wide strip of film is rolled once against a smooth stainlesssteel surface at a rate of 12 inches (30.5 cm) per minute using a 4.5pound (2.04 kg) roller and then tested as having a peak adhesion peelforce value ranging from about 1 to about 50 ounces/inch (0.012 to 0.600kg/cm), more preferably from about 1 to about 2.5 ounces/inch (0.012 to0.027 kg/cm) of strip width. In general, minimum adhesion whichmaintains a seal is desired for a storage wrap, so that the wrap iseasily peeled open for access to the stored item(s).

In a preferred embodiment, the improved storage wrap material of thepresent invention is a substantially clingless wrap material in contrastto typical commercially-available storage wrap materials. As discussedabove, such materials exhibit “cling” properties on a constant basis,such that they cling to themselves and to other surfaces wheneverbrought into proximity with them, whether desirable or not. Suchmaterials often incorporate resins, additives, tackifiers, or othermaterials to achieve the target level of cling. Suitable methods ofmeasuring and quantifying this cling property are described in ASTM testmethods D5458-95 and D3354-89. Test method D5458-95 is useful formeasuring cling between two layers of film in both stretched andunstretched conditions, and utilizes a 1 inch wide film strip adhered toa flat film attached to an inclined surface. The force required toremove the film strip from the flat film is measured. Test methodD3354-89 is useful for measuring the degree of blocking (unwantedadhesion) existing between overlapping layers of plastic film.Film-to-film adhesion is expressed as a blocking load in grams whichwill cause two layers of polyethylene film to separate with an area ofcontact of 100 square centimeters.

Substantially clingless wrap materials in accordance with the presentinvention can be produced by proper selection of materials including theavoidance of any significant amount of materials known in the art as“cling additives”, including those of the types described above.Further, additional materials or additives can be incorporated as neededto further reduce, if not eliminate, the tendency of such materials tocling to themselves and other surfaces. Such materials would includeanti-static agents, etc.

The improved storage wrap materials of the present invention may takemany forms and may be manufactured by a variety of different approaches.One design category that can provide the required propertiesincorporates the use of standoffs to prevent an adhesive layer frommaking contact with external surfaces before intended to do so. Throughuser activation, the standoffs are designed to be deformable, removable,repositionable, or frangible in order to expose the adhesive, whenintended, to the target surface. One particular approach within thatdesign category which is believed to be presently preferred is to form athree-dimensional polymeric film structure with a layer ofpressure-sensitive adhesive protected from contact with other surfacesby integrally-formed deformable protrusions or stand-offs. To activatethe material, once the material is positioned over the desired targetsurface (which may be another portion of itself) the user exerts apressure on the desired location of the material to collapse theprotrusions and bring the adhesive into engagement with the targetsurface to form the desired bond. Such materials are described ingreater detail in commonly-assigned, co-pending U.S. patent applicationSer. No. 08/584,638, filed Jan. 10, 1996 in the names of Peter W.Hamilton and Kenneth S. McGuire, entitled “Composite Material ReleasablySealable To A Target Surface When Pressed Thereagainst and Method ofMaking”, the disclosure of which is hereby incorporated herein byreference.

If such a three-dimensional structure is used as a storage wrap inaccordance with the present invention, for example, the external contactsurfaces may be either compliant or rigid and planar or non-planar.Having the three dimensional structure deform is preferred for use witha rigid target surface. If the substance is adhesive and the objectiveis releasable adherence to a target surface after deformation of thestructure, then degree of adhesion is important. Inversion ofprotrusions, especially those made of HDPE, minimizes protrusion springback so that higher adhesion isn't necessary in order to prevent thefailure of relatively weak seals. In this embodiment it is desired thatthe protrusion remain “dead” or non-resilient after being inverted orcrushed; however, a resilient protrusion could be used, for example,where it is intended for the bond to be permanent, where aggressiveadhesive overcomes spring back. Also, a resilient protrusion may bedesirable where repeat use of the material is intended.

FIGS. 2-3 illustrates a typical storage wrap material 10 constructed inaccordance with the aforementioned Hamilton et al. application which issuitable for use as a storage wrap material of the present invention. Ina preferred embodiment, the three-dimensional protrusions depicted inFIGS. 2-3 may be formed in an amorphous pattern of two-dimensionalgeometrical shapes such that the sheet of material resists nesting ofsuperimposed layers such as would be encountered in a roll of product.Such three-dimensional, nesting-resistant materials and patterns aredescribed in greater detail in commonly-assigned, co-pending,concurrently-filed U.S. patent application Ser. No. ______, Attorney'sDocket No. Case 6356, filed Nov. 8, 1996 in the names of Kenneth S.McGuire, Richard Tweddell, III and Peter W. Hamilton, entitled“Three-Dimensional, Nesting-Resistant Sheet Materials and Method andApparatus for Making Same”, the disclosure of which is herebyincorporated herein by reference.

When the material is formed into an elongated web with the intention ofwinding it upon a mandrel or upon itself (core-less roll) for purposesof compact storage, in accordance with the present invention the webexhibits the non-uniform pattern at least in the direction of rolling,and most preferably in both the rolling direction and the cross-rollingdirection. While an infinitely non-repeating pattern may be desirablefor certain applications, at a minimum the materials of the presentinvention will exhibit a non-uniform pattern property for a web distanceat least as great as the maximum intended roll circumference of a rollof product.

In order to provide the greatest degree of nesting-resistance, thethree-dimensional, nesting-resistant sheet materials of the presentinvention preferably exhibit a two-dimensional pattern ofthree-dimensional protrusions which is substantially amorphous innature. As utilized herein, the term “amorphous” refers to a patternwhich exhibits no readily perceptible organization, regularity, ororientation of constituent elements. This definition of the term“amorphous” is generally in accordance with the ordinary meaning of theterm as evidenced by the corresponding definition in Webster's Ninth NewCollegiate Dictionary. In such a pattern, the orientation andarrangement of one element with regard to a neighboring element bear nopredictable relationship to that of the next succeeding element(s)beyond.

By way of contrast, the term “array” is utilized herein to refer topatterns of constituent elements which exhibit a regular, orderedgrouping or arrangement. This definition of the term “array” is likewisegenerally in accordance with the ordinary meaning of the term asevidenced by the corresponding definition in Webster's Ninth NewCollegiate Dictionary. In such an array pattern, the orientation andarrangement of one element with regard to a neighboring element bear apredictable relationship to that of the next succeeding element(s)beyond.

The degree to which order is present in an array pattern ofthree-dimensional protrusions bears a direct relationship to the degreeof nestability exhibited by the web. For example, in a highly-orderedarray pattern of uniformly-sized and shaped hollow protrusions in aclose-packed hexagonal array, each protrusion is literally a repeat ofany other protrusion. Nesting of regions of such a web, if not in factthe entire web, can be achieved with a web alignment shift betweensuperimposed webs or web portions of no more than one protrusion-spacingin any given direction. Lesser degrees of order may demonstrate lessnesting tendency, although any degree of order is believed to providesome degree of nestability. Accordingly, an amorphous, non-orderedpattern of protrusions would therefore exhibit the greatest possibledegree of nesting-resistance.

While it is presently preferred that the entire surface of a web inaccordance with the present invention exhibit such an amorphous pattern,under some circumstances it may be desirable for less than the entiresurface of such a web to exhibit such a pattern. For example, acomparatively small portion of the web may exhibit some regular patternof protrusions or may in fact be free of protrusions so as to present agenerally planar surface. In addition, wherein the sheet material is tobe formed as a comparatively large sheet of material and/or as anelongated continuous web to be folded or wound upon itself,manufacturing constraints may require that the amorphous pattern itselfbe repeated periodically within the web. Although any pattern repetitionwithin the web allows some possibility of nesting occurring, such apossibility only exists when precise alignment of superimposed webs orweb portions occurs with such webs or web portions representing exactlyone repeat of the pattern (or an integer number of repeats for acontinuous wound or folded web). This contrasts with the nestingcharacter of webs formed of uniformly-shaped protrusions in an arraypattern wherein each protrusion is a repeat of the adjacent protrusionssuch that the repeat distance is a single protrusion spacing. In such aconfiguration, alignment for nesting would occur if web alignment occurswith a shift of no more than one protrusion-spacing.

In a web with an amorphous pattern of three-dimensional protrusions, anyselection of an adjacent plurality of protrusions will be unique withinthe scope of the pattern, even though under some circumstances it isconceivable that a given individual protrusion may possibly not beunique within the scope of the pattern. By utilizing an amorphouspattern, the three-dimensional sheet of material (in the case of a sheethaving hollow, three-dimensional protrusions) will not nest unlessprecise superposition of sheets of material having the same amorphouspattern occurs.

Three-dimensional sheet materials having a two-dimensional pattern ofthree-dimensional protrusions which is substantially amorphous in natureare also believed to exhibit “isomorphism”. As utilized herein, theterms “isomorphism” and its root “isomorphic” are utilized to refer tosubstantial uniformity in geometrical and structural properties for agiven circumscribed area wherever such an area is delineated within thepattern. This definition of the term “isomorphic” is generally inaccordance with the ordinary meaning of the term as evidenced by thecorresponding definition in Webster's Ninth New Collegiate Dictionary.By way of example, a prescribed area comprising astatistically-significant number of protrusions with regard to theentire amorphous pattern would yield statistically substantiallyequivalent values for such web properties as protrusion area, numberdensity of protrusions, total protrusion wall length, etc. Such acorrelation is believed desirable with respect to physical, structuralweb properties when uniformity is desired across the web surface, andparticularly so with regard to web properties measured normal to theplane of the web such as crush-resistance of protrusions, etc.

Utilization of an amorphous pattern of three-dimensional protrusions hasother advantages as well. For example, it has been observed thatthree-dimensional sheet materials formed from a material which isinitially isotropic within the plane of the material remain generallyisotropic with respect to physical web properties in directions withinthe plane of the material. As utilized herein, the term “isotropic” isutilized to refer to web properties which are exhibited to substantiallyequal degrees in all directions within the plane of the material. Thisdefinition of the term “isotropic” is likewise generally in accordancewith the ordinary meaning of the term as evidenced by the correspondingdefinition in Webster's Ninth New Collegiate Dictionary. Without wishingto be bound by theory, this is presently believed to be due to thenon-ordered, non-oriented arrangement of the three-dimensionalprotrusions within the amorphous pattern. Conversely, directional webmaterials exhibiting web properties which vary by web direction willtypically exhibit such properties in similar fashion following theintroduction of the amorphous pattern upon the material. By way ofexample, such a sheet of material could exhibit substantially uniformtensile properties in any direction within the plane of the material ifthe starting material was isotropic in tensile properties.

Such an amorphous pattern in the physical sense translates into astatistically equivalent number of protrusions per unit length measureencountered by a line drawn in any given direction outwardly as a rayfrom any given point within the pattern. Other statistically equivalentparameters could include number of protrusion walls, average protrusionarea, average total space between protrusions, etc. Statisticalequivalence in terms of structural geometrical features with regard todirections in the plane of the web is believed to translate intostatistical equivalence in terms of directional web properties.

Revisiting the array concept to highlight the distinction between arraysand amorphous patterns, since an array is by definition “ordered” in thephysical sense it would exhibit some regularity in the size, shape,spacing, and/or orientation of protrusions. Accordingly, a line or raydrawn from a given point in the pattern would yield statisticallydifferent values depending upon the direction in which the ray extendsfor such parameters as number of protrusion walls, average protrusionarea, average total space between protrusions, etc. with a correspondingvariation in directional web properties.

Within the preferred amorphous pattern, protrusions will preferably benon-uniform with regard to their size, shape, orientation with respectto the web, and spacing between adjacent protrusion centers. Withoutwishing to be bound by theory, differences in center-to-center spacingof adjacent protrusions are believed to play an important role inreducing the likelihood of nesting occurring in the face-to-back nestingscenario. Differences in center-to-center spacing of protrusions withinthe pattern result in the physical sense in the spaces betweenprotrusions being located in different spatial locations with respect tothe overall web. Accordingly, the likelihood of a “match” occurringbetween superimposed portions of one or more webs in terms ofprotrusions/space locations is quite low. Further, the likelihood of a“match” occurring between a plurality of adjacent protrusions/spaces onsuperimposed webs or web portions is even lower due to the amorphousnature of the protrusion pattern.

In a completely amorphous pattern, as would be presently preferred, thecenter-to-center spacing is random, at least within a designer-specifiedbounded range, such that there is an equal likelihood of the nearestneighbor to a given protrusion occurring at any given angular positionwithin the plane of the web. Other physical geometrical characteristicsof the web are also preferably random, or at least non-uniform, withinthe boundary conditions of the pattern, such as the number of sides ofthe protrusions, angles included within each protrusion, size of theprotrusions, etc. However, while it is possible and in somecircumstances desirable to have the spacing between adjacent protrusionsbe non-uniform and/or random, the selection of polygon shapes which arecapable of interlocking together makes a uniform spacing betweenadjacent protrusions possible. This is particularly useful for someapplications of the three-dimensional, nesting-resistant sheet materialsof the present invention, as will be discussed hereafter.

A sheet or web of material can be intentionally created with a pluralityof amorphous areas within the same sheet or web, even to the point ofreplication of the same amorphous pattern in two or more such regions.The designer may purposely separate amorphous regions with a regulardefined, non-amorphous pattern or array, or even a “blank” region withno protrusions at all, or any combination thereof. The formationscontained within a non-amorphous area can be of any number density,height or shape. Further, the shape and dimensions of the non-amorphousregion itself can be customized as desired. Additional examples offormation shapes, but not intended to be exhaustive, are: wedgesemanating from a point; truncated wedges; polygons; circles; curvilinearshapes; or combinations thereof.

Additionally, a single amorphous region may fully envelop orcircumscribe one or more non-amorphous areas. An example is a single,continuous amorphous region with non-amorphous patterns fully enclosednear the center of the sheet or web. Such imbedded patterns maycommunicate brand name, the manufacturer, instructions, material side orface indication, other information or simply be decorative in nature.

Multiple non-amorphous regions may be abutted or overlapped in asubstantially contiguous manner to substantially divide one amorphouspattern into multiple regions or to separate multiple amorphous regionsthat were never part of a greater single amorphous region beforehand.

From the foregoing discussion it would be apparent that the utilizationof an amorphous pattern of three-dimensional protrusions enables thefabrication of webs having the advantages of an array pattern, forexample, statistical uniformity in web properties on an area/locationbasis, without the key disadvantages of using an array in suchapplications, namely nestability and anisotropism.

Webs according to the present invention may have protrusions formed ofvirtually any three-dimensional shape, and accordingly need not be allof a convex polygonal shape. However, it is presently preferred to formthe protrusions in the shape of substantially-equal-height frustumshaving convex polygonal bases in the plane of one surface of thematerial and having interlocking, adjacent parallel sidewalls. For otherapplications, however, the protrusions need not necessarily be ofpolygonal shape.

As used herein, the term “polygon” (and the adjective form “polygonal”)is utilized to refer to a two-dimensional geometrical figure with threeor more sides, since a polygon with one or two sides would define aline. Accordingly, triangles, quadrilaterals, pentagons, hexagons, etc.are included within the term “polygon”, as would curvilinear shapes suchas circles, ellipses, etc. which would have an infinite number of sides.

When designing a three-dimensional structure, the desired physicalproperties of the resulting structure will dictate the size, geometricalshape, and spacing of the three-dimensional topographical features aswell as the choice of materials and forming techniques. For example,deformable three-dimensional protrusions will typically exhibit varyingdegrees of deformabilty, particularly crushability, depending upon theircross-sectional shape and average equivalent diameter. The bendingmodulus and/or flexibility of the overall web will depend upon therelative proportion of two-dimensional material betweenthree-dimensional protrusions.

When describing properties of three-dimensional structures ofnon-uniform, particularly non-circular, shapes and non-uniform spacing,it is often useful to utilize “average” quantities and/or “equivalent”quantities. For example, in terms of characterizing linear distancerelationships between three-dimensional protrusions in a two-dimensionalpattern, where spacings on a center-to-center basis or on an individualspacing basis, an “average” spacing term may be useful to characterizethe resulting structure. Other quantities that could be described interms of averages would include the proportion of surface area occupiedby protrusions, protrusion area, protrusion circumference, protrusiondiameter, etc. For other dimensions such as protrusion circumference andprotrusion diameter, an approximation can be made for protrusions whichare non-circular by constructing a hypothetical equivalent diameter asis often done in hydraulic contexts.

The three-dimensional shape of individual protrusions is believed toplay a role in determining both the physical properties of individualprotrusions as well as overall web properties. Of particular interestfor certain applications is crush resistance of protrusions (i.e., theirability to resist a deformation by crushing and/or inverting in adirection substantially perpendicular to the plane of the material).Without wishing to be bound by theory, it is presently believed that thecrush resistance of a given protrusion depends upon the crush strengthsof the individual panel segments which define each facet along theperimeter of the protrusion. The panel segment with the lowest crushstrength limits the crush strength of the protrusion, much as theweakest link defines the strength of a length of chain.

Buckling strengths of individual panels can be increased by introducingcurvature to the panel in a plane perpendicular to the crush direction,with buckling strength increasing with decreasing radius of curvature.Buckling strengths of individual panels may also be increased bydecreasing the width of the panel for a constant height (i.e.,decreasing the aspect ratio). In the case of non-curvilinear protrusionshaving a finite number of sides of substantially planar shape,application of these principles suggests that protrusions will exhibitgenerally greater crush resistance as the equality in side length andincluded angles increases by minimizing the “weakest link” effect.Accordingly, a protrusion with one side substantially longer than theothers will be limited in crush strength by the buckling behavior ofthat longest side. Therefore, crush strength for a given perimeter andgiven wall thickness would be greater for a protrusion having a greaternumber of smaller sides and would maximize its crush resistance byhaving the sides of substantially similar dimensions to minimize theweakest link effect.

It should be noted that the foregoing discussion assumes geometricreplication of three-dimensional structures from a forming structure ofgeometrically-sound shapes. “Real world” effects such as curvature,degree of moldability, radius of corners, etc. should be taken intoaccount with regard to ultimately exhibited physical properties.

The use of an interlocking network of frustums provides some sense ofuniformity to the overall web structure, which aids in the control anddesign of overall web properties such as web stretch, tensile strength,roll profile and thickness, etc., while maintaining the desired degreeof amorphousness in the pattern. In addition, when utilized as a basestructure for application of an adhesive or other active substance asdescribed in the above-referenced and incorporated commonly-assigned,co-pending U.S. patent application Ser. No. 08/584,638, the use of aninterlocking polygonal base pattern for the protrusions provides acontrollable width and spacing of the valleys between the protrusions sothat the area available for contact of the active agent with a targetsurface may be tailored. The use of external polygonal bases from whichthe sides of the frustums extend upwardly also add a degree ofpredictability and uniformity to the collapse of the protrusions undercompressive forces and also improves the release properties of theformed material from the corresponding forming structure.

The use of polygons having a finite number of sides in the amorphouspattern arranged in an interlocking relationship also provides anadvantage over structures employing circular or nearly-circular shapes.Patterns such as arrays employing closely-packed circles are limited interms of the amount of area the circles can occupy relative to thenon-circled area between adjacent circles. More specifically, even in apattern where adjacent circles touch at their point of tangency therewill still be a given amount of space “trapped” at the “corners” betweenconsecutive points of tangency. Accordingly, even amorphous patterns ofcircular shapes are limited in terms of how little non-circle area canbe designed into the structure. Conversely, interlocking polygonalshapes with finite numbers of sides (i.e., no shapes with curvilinearsides) can be designed so as to pack closely together and in thelimiting sense can be packed such that adjacent sides of adjacentpolygons can be in contact along their entire length such that there isno “trapped” free space between corners. Such patterns therefore open upthe entire possible range of polygon area from nearly 0% to nearly 100%,which may be particularly desirable for certain applications where thelow end of free space becomes important for functionality.

Any suitable method may be utilized to design the interlocking polygonalarrangement of hollow frustums which provides suitable design capabilityin terms of desirable protrusion size, shape, taper, spacing, repeatdistance, etc. Even manual methods of design may be utilized. Suchpattern may be imparted to the starting web material in any suitablefashion, including manual methods and methods of individuallycustom-forming the protrusions.

However, in accordance with the present invention, an expeditious methodof designing and forming such protrusions has been developed whichpermits the precise tailoring of desirable protrusion size, shape,taper, and spacing within an amorphous pattern, repeat distance of theamorphous pattern, etc. as well as the continuous formation of webscontaining such protrusions in an automated process.

A totally random pattern of three-dimensional hollow protrusions in aweb would, in theory, never exhibit face-to-back nesting since the shapeand alignment of each frustum would be unique. However, the design ofsuch a totally random pattern would be very time-consuming and complexproposition, as would be the method of manufacturing a suitable formingstructure. In accordance with the present invention, the non-nestingattributes may be obtained by designing patterns or structures where therelationship of adjacent cells or structures to one another isspecified, as is the overall geometrical character of the cells orstructures, but wherein the precise size, shape, and orientation of thecells or structures is non-uniform and non-repeating. The term“non-repeating”, as utilized herein, is intended to refer to patterns orstructures where an identical structure or shape is not present at anytwo locations within a defined area of interest. While there may be morethan one protrusion of a given size and shape within the pattern or areaof interest, the presence of other protrusions around them ofnon-uniform size and shape virtually eliminates the possibility of anidentical grouping of protrusions being present at multiple locations.Said differently, the pattern of protrusions is non-uniform throughoutthe area of interest such that no grouping of protrusions within theoverall pattern will be the same as any other like grouping ofprotrusions. The beam strength of the three-dimensional sheet materialwill prevent significant nesting of any region of material surrounding agiven protrusion even in the event that that protrusion finds itselfsuperimposed over a single matching depression since the protrusionssurrounding the single protrusion of interest will differ in size,shape, and resultant center-to-center spacing from those surrounding theother protrusion/depression.

Professor Davies of the University of Manchester has been studyingporous cellular ceramic membranes and, more particularly, has beengenerating analytical models of such membranes to permit mathematicalmodeling to simulate real-world performance. This work was described ingreater detail in a publication entitled “Porous cellular ceramicmembranes: a stochastic model to describe the structure of an anodicoxide membrane”, authored by J. Broughton and G. A. Davies, whichappeared in the Journal of Membrane Science, Vol. 106 (1995), at pp.89-101, the disclosure of which is hereby incorporated herein byreference. Other related mathematical modeling techniques are describedin greater detail in “Computing the n-dimensional Delaunay tessellationwith application to Voronoi polytopes”, authored by D. F. Watson, whichappeared in The Computer Journal, Vol. 24, No. 2 (1981), at pp. 167-172,and “Statistical Models to Describe the Structure of Porous CeramicMembranes”, authored by J. F. F. Lim, X. Jia, R. Jafferali, and G. A.Davies, which appeared in Separation Science and Technology, 28(1-3)(1993) at pp. 821-854, the disclosures of both of which are herebyincorporated herein by reference.

As part of this work, Professor Davies developed a two-dimensionalpolygonal pattern based upon a constrained Voronoi tessellation of2-space. In such a method, again with reference to the above-identifiedpublication, nucleation points are placed in random positions in abounded (pre-determined) plane which are equal in number to the numberof polygons desired in the finished pattern. A computer program “grows”each point as a circle simultaneously and radially from each nucleationpoint at equal rates. As growth fronts from neighboring nucleationpoints meet, growth stops and a boundary line is formed. These boundarylines each form the edge of a polygon, with vertices formed byintersections of boundary lines.

While this theoretical background is useful in understanding how suchpatterns may be generated and the properties of such patterns, thereremains the issue of performing the above numerical repetitionsstep-wise to propagate the nucleation points outwardly throughout thedesired field of interest to completion. Accordingly, to expeditiouslycarry out this process a computer program is preferably written toperform these calculations given the appropriate boundary conditions andinput parameters and deliver the desired output.

The first step in generating a pattern for making a three-dimensionalforming structure is to establish the dimensions of the desired formingstructure. For example, if it is desired to construct a formingstructure 8 inches wide and 10 inches long, for optionally forming intoa drum or belt as well as a plate, then an X-Y coordinate system isestablished with the maximum X dimension (X_(Max)) being 8 inches andthe maximum Y dimension (Y_(Max)) being 10 inches (or vice-versa).

After the coordinate system and maximum dimensions are specified, thenext step is to determine the number of “nucleation points” which willbecome polygons corresponding to the number of protrusions desiredwithin the defined boundaries of the forming structure. This number isan integer between 0 and infinity, and should be selected with regard tothe average size and spacing of the polygons desired in the finishedpattern. Larger numbers correspond to smaller polygons, and vice-versa.A useful approach to determining the appropriate number of nucleationpoints or polygons is to compute the number of polygons of anartificial, hypothetical, uniform size and shape that would be requiredto fill the desired forming structure. Assuming common units ofmeasurement, the forming structure area (length times width) divided bythe square of the sum of the polygon diameter and the spacing betweenpolygons will yield the desired numerical value N (rounded to thenearest integer). This formula in equation form would be:

$N = \frac{X_{Max}Y_{Max}}{\left( {{{polygon}\mspace{14mu} {size}} + {{polygon}\mspace{11mu} {spacing}}} \right)^{2}}$

A random number generator is required for the next step. Any suitablerandom number generator known to those skilled in the art may beutilized, including those requiring a “seed number” or utilizing anobjectively determined starting value such as chronological time. Manyrandom number generators operate to provide a number between zero andone (0-1), and the discussion hereafter assumes the use of such agenerator. A generator with differing output may also be utilized if theresult is converted to some number between zero and one or ifappropriate conversion factors are utilized.

A computer program is written to run the random number generator thedesired number of iterations to generate as many random numbers as isrequired to equal twice the desired number of “nucleation points”calculated above. As the numbers are generated, alternate numbers aremultiplied by either the maximum X dimension or the maximum Y dimensionto generate random pairs of X and Y coordinates all having X valuesbetween zero and the maximum X dimension and Y values between zero andthe maximum Y dimension. These values are then stored as pairs of (X,Y)coordinates equal in number to the number of “nucleation points”.

If the method described in the preceding paragraph is utilized togenerate a resulting pattern, the pattern will be truly random. Thistruly random pattern will, by its nature, have a large distribution ofpolygon sizes and shapes which may be undesirable in some instances. Forexample, a large distribution of polygon sizes may lead to largevariations in web properties in various regions of the web and may leadto difficulties in forming the web depending upon the formation methodselected. In order to provide some degree of control over the degree ofrandomness associated with the generation of “nucleation point”locations, a control factor or “constraint” is chosen and referred tohereafter as β (beta). The constraint limits the proximity ofneighboring nucleation point locations through the introduction of anexclusion distance, E, which represents the minimum distance between anytwo adjacent nucleation points. The exclusion distance E is computed asfollows:

$E = \frac{2\beta}{\sqrt{\lambda\pi}}$

where λ (lambda) is the number density of points (points per unit area)and β ranges from 0 to 1.

To implement the control of the “degree of randomness”, the firstnucleation point is placed as described above. β is then selected, and Eis calculated from the above equation. Note that β, and thus E, willremain constant throughout the placement of nucleation points. For everysubsequent nucleation point (X,Y) coordinate that is generated, thedistance from this point is computed to every other nucleation pointthat has already been placed. If this distance is less than E for anypoint, the newly-generated (X,Y) coordinates are deleted and a new setis generated. This process is repeated until all N points have beensuccessfully placed. If β=0, then the exclusion distance is zero, andthe pattern will be truly random. If β=1, the exclusion distance isequal to the nearest neighbor distance for a hexagonally close-packedarray. Selecting β between 0 and 1 allows control over the “degree ofrandomness” between these two extremes.

Once the complete set of nucleation points are computed and stored, aDelaunay triangulation is performed as the precursor step to generatingthe finished polygonal pattern. The use of a Delaunay triangulation inthis process constitutes a simpler but mathematically equivalentalternative to iteratively “growing” the polygons from the nucleationpoints simultaneously as circles, as described in the theoretical modelabove. The theme behind performing the triangulation is to generate setsof three nucleation points forming triangles, such that a circleconstructed to pass through those three points will not include anyother nucleation points within the circle. To perform the Delaunaytriangulation, a computer program is written to assemble every possiblecombination of three nucleation points, with each nucleation point beingassigned a unique number (integer) merely for identification purposes.The radius and center point coordinates are then calculated for a circlepassing through each set of three triangularly-arranged points. Thecoordinate locations of each nucleation point not used to define theparticular triangle are then compared with the coordinates of the circle(radius and center point) to determine whether any of the othernucleation points fall within the circle of the three points ofinterest. If the constructed circle for those three points passes thetest (no other nucleation points falling within the circle), then thethree point numbers, their X and Y coordinates, the radius of thecircle, and the X and Y coordinates of the circle center are stored. Ifthe constructed circle for those three points fails the test, no resultsare saved and the calculation progresses to the next set of threepoints.

Once the Delaunay triangulation has been completed, a Voronoitessellation of 2-space is then performed to generate the finishedpolygons. To accomplish the tessellation, each nucleation point saved asbeing a vertex of a Delaunay triangle forms the center of a polygon. Theoutline of the polygon is then constructed by sequentially connectingthe center points of the circumscribed circles of each of the Delaunaytriangles, which include that vertex, sequentially in clockwise fashion.Saving these circle center points in a repetitive order such asclockwise enables the coordinates of the vertices of each polygon to bestored sequentially throughout the field of nucleation points. Ingenerating the polygons, a comparison is made such that any trianglevertices at the boundaries of the pattern are omitted from thecalculation since they will not define a complete polygon.

Once a finished pattern of interlocking polygonal two-dimensional shapesis generated, in accordance with the present invention such a network ofinterlocking shapes is utilized as the design for one web surface of aweb of material with the pattern defining the shapes of the bases of thethree-dimensional, hollow protrusions formed from the initially planarweb of starting material. In order to accomplish this formation ofprotrusions from an initially planar web of starting material, asuitable forming structure comprising a negative of the desired finishedthree-dimensional structure is created which the starting material iscaused to conform to by exerting suitable forces sufficient topermanently deform the starting material.

From the completed data file of polygon vertex coordinates, a physicaloutput such as a line drawing may be made of the finished pattern ofpolygons. This pattern may be utilized in conventional fashion as theinput pattern for a metal screen etching process to form athree-dimensional forming structure suitable for forming the materialsof the present invention. If a greater spacing between the polygons isdesired, a computer program can be written to add one or more parallellines to each polygon side to increase their width (and hence decreasethe size of the polygons a corresponding amount).

Preferably, the computer program described above provides as its outputa computer graphic (.TIFF) file. From this data file, a photographicnegative can be made for use in a photoetching process to etch negativeimpressions into a base material to correspond to the desired frustumpolygonal shapes in the finished web of material. Alternatively,depending upon the desired process of generating the negative formingstructure for forming the finished web, it may be desirable to tailorthe output of the computer program to deliver coordinate points, etc. ofthe polygonal recesses, such as would prove useful if a mechanicalprocess were to be utilized. In addition, if it were desirable to form amale pattern the computer output could be tailored to provide thedesired information to the forming apparatus to the extent it may differthan for a negative (female) pattern.

To provide further illustration of the effect of increasing levels ofconstraint obtained by various values of β, an exemplary β value of 0.25(i.e., in the lower end of the range of 0 to 1) yields a much greatervariation in the center-to-center spacing of the nucleation points andthus the resulting polygons than does an exemplary β value of 0.75(i.e., near the higher end of the range of 0 to 1). Such degree ofvariation in center-to-center spacing also in the geometrical sensetranslates into a corresponding degree of variation in number of sidesin the resulting polygons as well as polygon size, the effects of whichwere discussed above. In order to produce the desired level ofamorphousness in the resulting pattern of polygons, the value presentlypreferred for β is 0.75, but this value may of course be tailored asrequired to suit a particular application.

The polygon area distribution decreases as the constraint (β) isincreased. Said differently, the less constrained pattern exhibits abroader range of polygon sizes than the more constrained pattern.Moreover, for a given sample “test box” drawn within the pattern, achange in the area of the test box affects the range of % polygon arefor a given pattern. As the area of the test box decreases, thevariability in % polygon area increases. Conversely, as the area of thetest box increases, beyond a certain point the % polygon area remainsconstant throughout the pattern. The more constrained material of(larger β) displays a much narrower range of % polygon area andconverges to a constant % polygon area at a smaller test box size than aless constrained material. Further, for consistency in physicalproperties throughout the web more constrained tessellations exhibitless variation in aerial density, i.e., the localized number ofprotrusions and corresponding protrusions wells, per unit area.

Based upon these observations, it would be apparent that a predictablelevel of consistency may be designed into the patterns generatedaccording to the preferred method of the present invention even thoughamorphousness within the pattern is preserved. Accordingly,three-dimensional, amorphous-patterned, nesting-resistant materials maybe formed with statistically-predictable geometric and physical materialproperties.

Referring once again to the drawings, and more particularly to FIG. 2,there is shown a plan view of a representative three-dimensional,nesting-resistant sheet material suitable for use as a storage wrapmaterial of the present invention, which is generally indicated as 10.FIG. 2 represents an amorphous two-dimensional pattern generated by theabove-described method utilizing a constraint factor of 0.75. Material10 has a plurality of non-uniformly shaped and sized, preferably hollow,protrusions 12, surrounded by spaces or valleys 14 therebetween, whichare preferably interconnected to form a continuous network of spaceswithin the amorphous pattern. FIG. 2 also shows a dimension A, whichrepresents the width of spaces 14, measured as the substantiallyperpendicular distance between adjacent, substantially parallel walls atthe base of the protrusions. In a preferred embodiment, the width ofspaces 14 is preferably substantially constant throughout the pattern ofprotrusions.

Protrusions 12 of the present invention are generated with non-uniformsize and shape so that material 10 may be wound onto a roll withoutnesting occurring between layers of material within the roll. Thenesting-resistant feature is achieved because the amorphous pattern ofthe protrusions, as discussed above, limits the ability of the face ofone layer to align with the back of another layer whereby theprotrusions of one layer enter the depressions formed behind eachprotrusion in an adjacent layer. The benefit of narrow constant-widthspaces between protrusions is that protrusions 12 cannot also enterspaces 14 when layers of material 10 are placed face to face.

Protrusions 14 are preferably spaced center to center an averagedistance of approximately two protrusion base diameters or closer, inorder to minimize the volume of valleys between protrusions and hencethe amount of substance located between them. For applications where itis intended that the protrusions be deformable, the protrusions 14preferably have heights which are less than their diameters, so thatwhen they deform, they deform by substantially inverting and/or crushingalong an axis which is substantially perpendicular to a plane of thematerial. This protrusion shape and mode of deforming discouragesprotrusions 14 from folding over in a direction parallel to a plane ofthe material so that the protrusions cannot block a substance present inthe valley between them from contact with a target surface.

FIG. 3 depicts a fragmentary elevational cross-section of material 10taken at a location where a complete protrusion 12 and both adjoiningspaces or valleys 14 can be seen in cross-section. In this view, theupper surface of the web which faces the viewer of FIG. 2, and whichincludes the projecting portions of the protrusions 12, is identifiedwith the numeral 15, and is referred to hereafter as the male side ofthe material. Correspondingly, the lower surface of the web facing awayfrom the viewer of FIG. 2, which includes the openings of the hollowportions of the protrusions 12, is identified with the numeral 17, andis referred to hereafter as the female side of the material.

FIG. 3 shows a substance 16 added to spaces 14, as well as to the hollowunderside of the protrusions 12, in accordance with the teachings ofcommonly-assigned, co-pending, concurrently-filed U.S. patentapplication Ser. No. 08/745,340, Attorney's Docket No. Case 5922R, filedNov. 8, 1996, in the names of Peter W. Hamilton and Kenneth S. McGuire,entitled “Material Having A Substance Protected by Deformable Standoffsand Method of Making”, the disclosure of which is hereby incorporatedherein by reference. Substance 16 partially fills the spaces 14 so thatan outer surface of protrusions 12 remain external to the surface levelof substance 16 such that the protrusions prevent the substance 16 onthe male side of the material from making contact with externalsurfaces. With regard to the male side of the material, substance 16partially fills the hollow protrusions such that the reverse side of thevalleys or spaces between respective protrusions serves an analogousfunction in preventing substance 16 within the protrusions from makingcontact with external surfaces. Substances within different sides of thematerial 10 and/or within different geometrically-distinct zones withina side of material 10 need not be the same substance and could in factbe distinctly different substances serving distinctly differentfunctions.

“Substance” is defined in this invention as any material capable ofbeing held in open valleys and/or depressions of a three dimensionalstructure. In the present invention, the term “substance” can mean aflowable substance which is substantially non-flowing prior to deliveryto a target surface. “Substance” can also mean a material which doesn'tflow at all, such as a fibrous or other interlocking material.“Substance” may mean a fluid or a solid. Adhesives, electrostatics,mechanical interlocking, capillary attraction, surface adsorption, andfriction, for example, may be used to hold the substances in the valleysand/or depressions. The substances may be permanently held in thevalleys and/or depressions, or the substances may be intended to bereleased therefrom when exposed to contact with external surfaces orwhen the three dimensional structure is deformed, heated, or otherwiseactivated. Of current interest in the present invention includesubstances such as gels, pastes, foams, powders, agglomerated particles,prills, microencapsulated liquids, waxes, suspensions, liquids, andcombinations thereof.

The spaces in the three-dimensional structure of the present inventionare normally open; therefore it is desirable to have substances stay inplace and not run out of the structure without an activation step. Theactivation step of the present invention is preferably deformation ofthe three-dimensional structure by compression. However, an activationstep to cause substance to flow could be heating the material to aboveroom temperature or cooling it below room temperature. Or it couldinclude providing forces excessive of the earth's gravity. It could alsoinclude other deforming forces, such as tensile forces and combinationsof these activation phenomena.

The term “deformable material” is intended to include foils, polymersheets, cloth, wovens or nonwovens, paper, cellulose fiber sheets,co-extrusions, laminates, and combinations thereof. The properties of aselected deformable material can include, though are not restricted to,combinations or degrees of being: porous, non-porous, microporous, gasor liquid permeable, non-permeable, hydrophilic, hydrophobic,hydroscopic, oleophilic, oleophobic, high critical surface tension, lowcritical surface tension, surface pre-textured, elastically yieldable,plastically yieldable, electrically conductive, and electricallynon-conductive. Exemplary materials include wood, metal, rigid polymerstock, ceramic, glass, cured resin, thermoset materials, cross-linkedmaterials, rubber, frozen liquids, concrete, cement, stone, man-madematerials, etc. Such materials can be homogeneous or compositioncombinations.

In a particularly preferred embodiment, protrusions 14 have an averagebase diameter of about 0.015 inches (0.038 cm) to about 0.030 inches(0.076 cm), and more preferably about 0.025 inches (0.064 cm). They alsohave an average center-to-center spacing of from 0.03 inches (0.08 cm)to 0.06 inches (0.15 cm), and more preferably about 0.05 inches (0.13cm) spacing. This results in a high number density of protrusions. Themore protrusions per unit area, the thinner the piece of material andprotrusion walls can be in order to resist a given deformation force. Ina preferred embodiment the number of protrusions per square inch exceeds200 and the protrusions occupy from about 30% to about 70% of theprotrusion side of the piece of maternal. They have a protrusion heightof about 0.004 inches (0.010 cm) to 0.012 inches (0.030 cm), and morepreferably about 0.006 inches (0.015 cm) height. The preferred materialis 0.0003 inch (0.0076 mm) nominal thickness high density polyethylene(HDPE).

For fabrication of an adhesive-containing, three-dimensional,nesting-resistant sheet material, a preferred layer of substance 16 ispreferably a latex pressure sensitive adhesive about 0.001 inch (0.025mm) thick. Even more preferably, layer of substance 16 may be about0.0005 inch (0.013 mm) thick layer to about 0.002 inch (0.051 mm) thicklayer of hot melt adhesive, specification no. Fuller HL-2115X, made byH. B. Fuller Co. of Vadnais Heights, Minn. Any adhesive can be usedwhich suits the needs of the material application. Adhesives may berefastenable, releasable, permanent, or otherwise. The size and spacingof protrusions is preferably selected to provide a continuous adhesivepath surrounding protrusions so that air-tight seals may be made with atarget surface.

Film materials may be made from homogeneous resins or blends thereof.Single or multiple layers within the film structure are contemplated,whether co-extruded, extrusion-coated, laminated or combined by otherknown means. The key attribute of the film material is that it beformable to produce protrusions and valleys. Useful resins includepolyethylene, polypropylene, PET, PVC, PVDC, latex structures, nylon,etc. Polyolefins are generally preferred due to their lower cost andease of forming. Preferred material gauges are about 0.0001 inches(0.0025 mm) to about 0.010 inches (0.25 mm). More preferred gauges arefrom about 0.0002 inches (0.005 mm) to about 0.002 inches (0.051 mm).Even more preferred gauges are from about 0.0003 inches (0.0076 mm) toabout 0.001 inches (0.025 mm).

Providing a film modulus of elasticity sufficiently high to minimizefilm stretch during use is beneficial to sealing material 10 to a targetsurface. Stretched film results in residual forces parallel to the planeof adhesive contact, which may cause a weak adhesive bond to break. Thelarger and more closely spaced the protrusions, the greater thelikelihood of stretch occurring in a given film. Although elasticity inmaterial 10 is believed to be undesirable for use as a container wrapwhich seals to a container, there are potentially many other uses for anelastic material containing a pattern of substance. Reducing theprotrusion spacing to the closest possible spacing which ismanufacturable may increase material stretch, but it may be beneficialin reducing the volume of substance between protrusions. Differentapplications for the formed material of the present invention willdictate ideal size and density of protrusions, as well as the selectionof the substances used therewith.

The material property “beam strength” of the three-dimensional sheetmaterial was mentioned above in terms of the beam strength preventingsignificant nesting of any region of material surrounding a givenprotrusion even in the event that that protrusion finds itselfsuperimposed over a single matching or larger depression of compatibleshape since the protrusions surrounding the single protrusion ofinterest will differ in size, shape, and spacing from those surroundingthe other protrusion/depression. Beam strength is thus an importantfactor to consider when selecting the material type and thickness, aswell as the density and pattern of protrusions. It has been observedthat in general larger numbers of smaller protrusions provide a greaterlevel of beam strength for a given material type and thickness than asmaller number of larger protrusions. Said differently, thinner and moreconformable materials may be utilized and still realize the non-nestingadvantages of the present invention through the use of an amorphouspattern having generally comparatively small, comparatively high numberdensity protrusions.

It is believed that the protrusion size, shape and spacing, the webmaterial properties such as flexural modulus, material stiffness,material thickness, hardness, deflection temperature as well as theforming process determine the strength of the protrusion. The formingprocess is important in polymer films for example, since “cold forming”or embossing generates residual stresses and different wall thicknessdistributions than that produced by thermoforming at elevatedtemperatures. For some applications it is desirable to provide astiffness (deformation resistance) which is sufficient to withstand apressure of at least 0.1 pounds per square inch (0.69 kPa) withoutsubstantially deforming protrusions to where the substance contacts anexternal surface. An example of this requirement would be the need towind the web onto a roll for transport and/or dispensing. Even with verylow in-wound pressures of 0.1 pounds per square inch (0.69 kPa), aresidual in-wound pressure in the interior of the roll may deformprotrusions in the web sufficiently to bring the overlaying web layersinto contact with the substance. A “threshold” protrusion stiffness isrequired to prevent this winding damage from occurring. Similarly, whenthe web is stored or dispensed as discrete sheets, this “threshold”stiffness is required to prevent premature activation of the product dueto the weight of overlaying layers of sheets or other forces, such asforces induced by shipping vibrations, mishandling, dropping and thelike.

Deformation mode and force can be influenced by the sidewall thicknessprofile to provide more desired results. A protrusion's sidewallconnects the outermost portion of the protrusion to the unformedmaterial adjacent to base perimeter of the protrusion. The sidewall asdefined may also contain a peripheral region substantially within theoutermost portion which is substantially thinner than the interiorregion of the outermost portion. Protrusions where at least a portion ofthe sidewalls are substantially thinner than the unformed materialadjacent to the base perimeter are believed preferred for deformation bythe user. Sidewalls that are also substantially thinner in at least aportion of the sidewall as compared to the material at the outermostportion of the protrusion also beneficially bias the deformation tooccur primarily within the sidewall structure.

In structures containing relatively small protrusions, as found in highnumber density protrusion patterns, such thinner sidewall gauges can beparticularly useful.

Protrusions 12 have sidewalls 22, which become thinned when protrusions12 are formed, to help ensure that protrusions 12 deform as intended.High density polyethylene is preferred over low density polyethylenebecause the former can be made thinner for the same protrusion deformstrength and because once deformed, HDPE protrusions do not tend torebound toward their undeformed initial configuration as do the LDPEprotrusions.

Protrusions 12 preferably have a convex polygonal base shape, theformation of which is described hereinafter. By convex polygonal shape,it is meant that the bases of the protrusions have multiple (three ormore) linear sides, which form no externally measured angle of less than180° with any adjacent side. Of course, alternative base shapes areequally useful. However, the preferred base shape is believed to be mosteasily generated. Polygons preferably interlock in the plane of thelower or female surface 17, as in a tessellation, to provide constantwidth spacing between them. The width A of spaces 14 may be selecteddepending upon the volume of substance desired between protrusions.Preferably width A is always less than the minimum protrusion dimensionof any of plurality of protrusions 12. The area occupied by plurality ofprotrusions 12 is preferably from about 30% to about 70%, morepreferably about 50%, of the available area of sheet of material 10, asmeasured parallel to plane 20.

FIGS. 4-6 disclose a suitable method and apparatus for making material10, the method generally indicated as 30. Method 30 is representativeand may be modified or tailored to suit a particular size, composition,etc. of the resulting material 10. Method 30 utilizes a forming surface32, which is preferably a three-dimensional screen having recesses 34and lands 36 between recesses 34. Such a forming structure or formingstructure would constitute a female-type forming structure which, inuse, would form corresponding male protrusions in thestructure-contacting side of the formed material. Alternatively, formingsurface 32 could comprise a three-dimensional forming structure of themale variety by having raised pins 34 of the desired polygonal shapehaving recesses 36 between and around the pins 34. In use, such aforming structure would form corresponding female depressions in thestructure-contacting side of the formed material.

More particularly, FIG. 4 depicts a forming surface which could beutilized to form a corresponding three-dimensional material 10 such asdepicted in FIG. 2. When a material 10 is thermoformed over formingsurface 32, protrusions 12 are preferably formed by drawing them intorecesses 34 with vacuum when material 10 is heated to a softeningtemperature, and then maintaining protrusions 12 drawn into recesses 34while material 10 cools to a solidification temperature. In this method,lands 36 define the bases of spaces 14 between protrusions 12.Protrusions 12 are preferably formed with sidewalls 22 being as nearlyperpendicular to plane 20 as possible, but with some taper beingtypical. Outermost ends of protrusions 12 may domed or more truncated inshape so as to form frustums of the corresponding polygonal shape.

Material 10 may be vacuum thermoformed, embossed, or hydroformed, orformed by other forming means commonly known in the art for permanentlydeforming thin materials.

FIG. 4 shows a preferred forming screen 32 comprising interconnectedlands 36 surrounding polygonal recesses 34. Lands 36 are preferably madeof stainless steel and coated with a release agent. Most preferably,screen 32 is made into a continuous belt 38, as shown in FIG. 6.Alternatively, screen 32 could be utilized in flat plate-like form orformed into a rigid drum. FIG. 5 depicts a partial cross-sectional viewof forming screen 32 taken at a location which depicts a cross-sectionthrough two consecutive lands. Lands 36 have a dimension B whichrepresents the land width, which is preferably constant as measuredbetween substantially parallel adjacent land edges, and a dimension Twhich represents screen thickness.

The amorphous pattern of the forming screen is preferably generated inaccordance with the method described above.

Methods of production can influence the sidewall thickness profile suchas in the use of a forming screen with essentially straight screen wallswhich define the forming screen hole. Such a process allows forsubstantially thinner sidewall thickness since the protrusion is freelydrawn from the base perimeter into the forming screen recess to thepoint of contact with the internal backup screen. The internal backupscreen's purpose is to prevent further drawing of the protrusion. Thisapproach yields a more varied gauge profile within the sidewalls.

It has been discovered while reducing to practice the present inventionthat when using hot melt adhesive for the substance, thermoformingbehaves differently than when other substances are processed. Thedifference is that protrusions, which are formed when hot melt adhesivehas been applied to the forming surface, tend to exhibit more thinningin their sidewalls. It is believed that the hot melt adhesive cools andsolidifies when contacting the metal forming surface and therebyprevents web material in contact with the adhesive from being drawn intothe recesses, so that uniform thickness valleys result. With othersubstances, such as latex adhesive, less thinning of protrusionsidewalls occurs, presumably because some of the web material in contactwith the adhesive on the lands or pin tops of the forming surface flowsinto the recesses during thermoforming.

FIG. 6 shows a suitable and presently preferred method and apparatus formaking a material such as material 10 of the present invention, which isgenerally indicated as 180. The formed material is preferablytransparent or translucent, so that it may be accurately positionedbefore being deformed. Transparency, however, introduces a new problemof determining on which side of the three-dimensional structure thesubstance is located, in order to know which side to place against atarget surface. Substance side identification can be solved by placingindicia on the surface of the three dimensional structure, by coloringthe substance a different tint than the three dimensional structure, orby providing a laminated material structure of different tints, forexample. In the case of labels, transparency may not be needed sincematerial edges may be used for proper positioning.

Micro-texturing the material during forming may also be useful, such asin producing a distinction between one side of the material and theother side. Micro-texturing of the outermost surface features of thethree dimensional structure may be achieved in the present invention,for example, by drawing the piece of material into forming screenrecesses and against a micro-textured surface, such as a vacuum drumhaving tiny apertures therein.

Forming screen 181 is threaded over idler pulley 182 and a driven vacuumroll 184. Forming screen 181 is preferably a 0.005 inch (0.013 cm)thick, 12.5 inch (31.8 cm) wide, 6 foot (183 cm) circumference stainlesssteel belt, having the desired protrusion pattern etched as recesses inthe belt. Covering the outer surface of vacuum roll 184 is a 195 meshseamless nickel screen having a diameter of 8.63 inches (21.9 cm), whichserves as a porous backing surface for forming screen 181.

For producing a pressure sensitive adhesive containing material, asubstance 186, preferably hot melt adhesive, is coated onto formingscreen 181 by a substance applicator 188 while forming screen 181travels at about 20 feet (610 cm) per minute. A material 190, forexample, a HDPE film web about 0.0005 inches (0.0013 cm) thick, isbrought into contact with the substance-coated forming screen atmaterial infeed idler roll 192. Hot air at approximately 600° F. (316°C.) and flowing at approximately 11.25 SCFM (0.32 cubic meters/minute)is directed radially at material 190 by a hot air source 194 as thematerial passes over vacuum roll 184 and as vacuum is applied to formingscreen 181 through vacuum roll 184 via fixed vacuum manifold 196 from avacuum source (not shown). A vacuum of approximately 12 inches ofmercury (40.6 kPa) is applied as the material is heated by hot airsource 194. A formed, substance coated material 198 is stripped fromforming screen 181 at stripping roll 200.

Stainless steel forming screen 181 is a fabricated, seamed belt. It isfabricated in several steps. The recess pattern is preferably developedby a computer program according to the method described above and ispreferably printed onto a transparency to provide a photomask forphotoetching. The photomask is used to create etched and non-etchedareas. The etched material is typically stainless steel, but it may alsobe brass, aluminum, copper, magnesium, and other materials includingalloys. Methods of making metal screens by photoetching are described inmore detail in commonly owned U.S. Pat. Nos. 4,342,314 to Radel andThompson, 4,508,256 to Radel et al., and 4,509,908 to Mullane, Jr., thedisclosures of which are hereby incorporated herein by reference.

Additionally, the recess pattern may be etched into photosensitivepolymers instead of metals. Examples are described along with a methodsof making polymer forming screens in commonly owned U.S. Pat. Nos.4,514,345 to Johnson et al., 5,098,522 to Smurkoski et al., 4,528,239 toTrokhan, and 5,245,025 to Trokhan, the disclosures of which are herebyincorporated herein by reference.

Next, the forming screen is converted into a continuous belt by buttwelding the ends together, using either laser or electron beam welding.This produces a nearly undetectable seam, which is needed to minimizedisruptions in the recess pattern. The final step is coating the endlessbelt with a low critical surface tension (non-stick) coating, such as aSeries 21000 proprietary release coating made by and applied by PlasmaCoatings of TN, Inc., located in Memphis, Tenn. It is believed that thiscoating is primarily an organo-silicone epoxy. As applied to a stainlesssteel forming screen used in the methods of the present invention, thiscoating provides a critical surface tension of about 18 dynes/cm. Othermaterials which may prove suitable for providing reduced criticalsurface tension include paraffins, silicones, PTFE's, and the like. Thiscoating allows the formed material to be removed from the belt withoutundue stretching or tearing.

A belt forming screen is believed advantageous to a flat plate or a drumforming screen because a belt enables screen patterns and patternlengths to be changed more easily and larger patterns may be usedwithout having massive rotating members. However, depending upon thedesired quantity and dimensions of the material 10 to be formed it maybe equally suitable to fabricate the forming structure as a flat plateor rigid drum, and/or other forming structures and methods known in theart.

Because the same common forming screen is used to transfer the substanceto the material as is used to form the protrusions, the substancepattern is conveniently registered with the protrusions. In thepreferred embodiment, the top surface of forming screen 32 is continuousexcept for recesses 34; thus, the substance pattern is totallyinterconnected in this configuration. However, if a discontinuouspattern of substance were coated onto forming screen 32, a discontinuoussubstance pattern between protrusions would result.

In accordance with the preferred method of manufacturing thethree-dimensional, nesting-resistant sheet material 10, thethree-dimensional protrusions are unitarily formed from the sheet ofdeformable material itself and are hollow structures with depressions inone side which preferably each have a size and three-dimensional shapecorresponding substantially with the size and three-dimensional shape oftheir respective protrusion. However, it may also be desirable for someapplications to utilize solid protrusions unitarily, integrally, orseparately formed from (and applied to) the sheet of material and whichmay or may not be deformable.

In general, the present invention is a storage wrap material which maytake the form of a three-dimensional sheet material which is activatedby applying a compressive force so that the structure collapses toexpose an adhesive to contact with external surface(s). However, thescope of the invention also applies to storage wrap materials which areactivatible by means other than compression. For example, the inventorshave found that a tensile force applied to the same three-dimensionalstructure can cause it to plastically deform longitudinally and therebycontract in caliper or thickness to similarly expose or releasesubstance. It is believed that under sufficient tension, the materialbetween protrusions deforms in response to forces in the plane of thematerial and that protrusions are thereby elongated in the samedirection. When the protrusions are elongated, they are reduced inheight. With enough elongation the protrusions are reduced in height towhere the substances between them, in them, or both are exposed.

For a one inch wide strip of material 10, made from 0.0003 inch (0.0076mm) thick HDPE and formed to have protrusions of 0.006 inches (0.152 mm)height and 0.030 inches (0.762 mm) diameter, spaced 0.045 inches (1.14mm) apart, the tensile force found necessary to cause protrusions toexpose a 0.001 inch (0.025 mm) thick coating of adhesive in the valleysbetween protrusions is approximately 0.80 pounds (0.36 kg) per inch ofstrip width.

A combination of compression and tensile forces may be applied to thematerial of the present invention in order to expose a substance fromwithin the three-dimensional structure. Although in a preferredembodiment of the present invention, the tensile force necessary toachieve sufficient deformation of said three-dimensional structure inorder to expose substance to an external surface is significantlygreater than a compressive force to achieve the same result, a structuremay be designed which is more easily deformed by a tensile force appliedin a specific planar direction. For example, a structure may haveparallel waves instead of protrusions and the waves may be easilyflattened by stretching the structure perpendicular to the waves but inthe plane of the waves. Tensile responsive structures and the principlesbehind them are disclosed in commonly-assigned U.S. Pat. No. 5,518,801to Chappell et al., the disclosure of which is hereby incorporatedherein by reference.

In another example, heat could be applied to cause the same structuremade of shrinkable film to reduce in thickness to similarly release orexpose the substance.

As described herein, different substances can be deposited on theopposing faces of the formed material. Multiple substances can belocated on the same face of the material either geometrically spacedfrom each other or commingled. Substances can be partially layered. Anexample is a layer of adhesive adjacent to the material surface with asolid particulate adhered to the exposed side of the adhesive layer. Inaddition, it is contemplated that it may be desirable for certainapplications to have protrusions extending outwardly from both sides ofthe formed material, such that both sides are active sides withdeformable protrusions.

A pattern of protrusions can be superimposed either on a similardimensional scale or on a different dimensional scale such as a singleor multiple “microprotrusion” pattern located on the tops of otherlarger protrusions.

Additional details of the process of FIG. 6, as well as additionaldetails regarding three-dimensional materials described above may befound in the aforementioned and incorporated commonly-assigned,co-pending, concurrently-filed U.S. patent application Ser. No.08/745,340, Attorney's Docket No. Case 5922R.

While under some circumstances it may be acceptable or desirable todesign the storage wrap material so as to form a discontinuous bondpattern with itself or another target surface, such as by having anintermittent or discontinuous layer of adhesive on its active surface,it is presently preferred that the storage wrap material be designed soas to exhibit the ability to form a continuous seal or bond with itselfand with any sufficiently continuous target surface.

FIGS. 7-9 depict representative applications of interest for the storagewrap material 10.

More particularly, FIG. 7 depicts storage wrap material 10 utilizedindependently to form a closed container for an item 60. For use in thisfashion, a one-sided version of storage wrap material 10 is preferablyutilized such that only one side of the material is active, although atwo-sided material could also be utilized. To utilize storage wrapmaterial 10 in this fashion, the material is wrapped or folded aroundthe desired item 60 so as to leave a marginal edge extending outwardlybeyond the maximum dimensions of the item 60. As depicted in FIG. 7, theweb of storage wrap material 10 has been folded over and around the item60 by folding the material along a folded edge 55 and forming a fin-typeseal 50 around the remaining perimeter, in this instance three sides, ofthe item 60. In this deployment, the storage wrap material 10 is bondedor adhered to itself in a face-to-face orientation wherein both activesides of the material are in contact with one another. Accordingly, whena user 70 activates the adhesive on at least one, and preferably both,of the overlying or overlapping portions of the material in the regionof the fin seal 50 the overlying portions are firmly adhered together tocomplete the enclosure of the item 60. Alternatively, rather thanfolding a larger web of material upon itself to form an enclosure, twoor more discrete smaller pieces of storage wrap material 10 may beutilized by wrapping them over the item 60 and sealing them to oneanother in face-to-face or face-to-back orientation.

FIG. 8 depicts another useful deployment of storage wrap material 10 asthe closure of a semi-enclosed, rigid or semi-rigid container 100. Inthe configuration of FIG. 8, a combination container structure is thusillustrated wherein the storage wrap material is adhered to the rimportion 105 of the container which circumscribes the opening 110 to forma corresponding closure for the opening. Although the storage wrapmaterial 10 would form an adequate barrier seal if only applied to thesurface of the rim 105 which is in the plane of the opening 110, asdepicted in FIG. 8 the storage wrap material 10 may also be applied soas to effect a seal over an additional area around the periphery of therim 105 by bonding to the wall portion 115 of the container whichextends in a direction substantially normal to the plane of the opening.Effective sealing may also be accomplished by bonding the storage wrapmaterial only to the wall portion 115 of the container. Where such aclosure completely encloses the contents (not shown) of the container100, the contents are protected from the exterior environment outsidethe container and are also contained and protected from loss.

Containers such as container 100, which as shown has no protrudingstructures for cooperating with storage wrap 10, are frequentlyconstructed of such rigid or semi-rigid materials such as metals, glass,ceramics, plastics, or wood which have a comparatively smooth anduniform surface. Accordingly, storage wrap material 10 in accordancewith the present invention activates to provide the desired level ofadhesive force in combination with such non-conforming, rigid orsemi-rigid surfaces so as to effectively form a closure for suchcontainers. In addition, the storage wrap material may also be utilizedin conjunction with openings in the plane of a wall of a container aswell as openings which are formed at an end, etc. of a containersubstantially normal to adjacent wall surfaces. Such versatility is dueto the adhesive properties of the storage wrap material which, unlikedead-fold wrap materials such as waxed paper or aluminum foil, enablethe storage wrap materials of the present invention to form a suitableseal without the need to form a wrap angle around a rim, lip, or otherstructure adjacent the container opening.

FIG. 9 depicts yet another common application for storage wrap 10,wherein a discrete web of storage wrap 10 of the desired dimensions iswrapped continuously around an item 60 so as to enclose the item 60completely. Edge portions 80 of the storage wrap 10 which overly theitem and overly other portions of the storage wrap 10 are adhered tosuch other portions after activation such that they are secured insealing relationship. This mode of item enclosure is particularly usefulwhen the item has an irregular shape, such as the item 60 depicted inFIG. 9. In this mode of deployment, the storage wrap 10 is preferablyoriented with the active side facing inwardly toward the item 60 suchthat the storage wrap may be activated over the item to provideadditional security against shifting or loosening of the material.Alternatively, the storage wrap 10 could be wrapped around the item withthe active side facing outwardly if adherence to the item is notdesired. In either mode of deployment, the overlying portions 80 of thestorage wrap material 10 will be activated and adhered to one another inface-to-back relation with one of the overlying portions being activatedto provide the adhesive property and the other overlying portion beingnon-activated and hence a passive target surface.

If a two-sided activatible storage wrap material were utilized in theabove example, then either or both of the superimposed face and backportions in the overlying portions 80 could be activated to effect asealed region.

The improved storage wrap materials of the present invention may beemployed to enclose a wide variety of items, both perishable andnon-perishable. Such items may include single items within a givencontainer/package system, as well as multiple items of the same ordifferent types. Items enclosed may in fact be containers or packageswhich are themselves to be enclosed, such as a group of cartons wrappedtogether upon a pallet, for example. The items may be loosely groupedtogether within a single chamber within the container, or may besegregated within different chambers or compartments formed by thestorage wrap material itself or other features of the container.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. An improved storage wrap material comprising: (a) a sheet ofnon-porous material having a first side and a second side, said firstside comprising an active side exhibiting an adhesion peel force afteractivation by a user which is greater than an adhesion peel forceexhibited prior to activation by a user and which is sufficient to forma continuous seal against a target surface, wherein a compressive forceof at least about 0.1 psi is required to activate said active side, andwherein said sheet of material is linerless, such that activation ofsaid active side requires no removal of components of said sheet ofmaterial, said sheet of material being sufficiently flexible to conformreadily to a desired surface and having sufficiently small resiliencythat it does not exert undue restorative forces which would tend tocause said sheet of material to break contact with such a desiredsurface.
 2. The improved storage wrap material of claim 1, wherein saidactive side is activatible by an externally applied force exerted uponsaid sheet of material.
 3. The improved storage wrap material of claim2, wherein said active side is activatible by an externally appliedcompressive force exerted in a direction substantially normal to saidsheet of material.
 4. The improved storage wrap material of claim 2,wherein said active side is activatible by an externally applied tensileforce exerted in a direction substantially parallel to said sheet ofmaterial.
 5. The improved storage wrap material of claim 1, wherein saidactive side exhibits an adhesion peel force of at least about 1 ounceper inch width after activation by a user.
 6. The improved storage wrapmaterial of claim 1, wherein said active side exhibits an adhesion peelforce of between about 1 and about 2.5 ounces per inch width afteractivation by a user.
 7. The improved storage wrap material of claim 1,wherein said active side may be selectively activated in discreteregions by a user.
 8. The improved storage wrap material of claim 1,wherein said active side may be activated by compression against atarget surface.
 9. The improved storage wrap material of claim 1,wherein said adhesion peel force after activation is sufficient to forma barrier seal against a target surface, said seal exhibiting barrierproperties at least as great as those of said material and said targetsurface.
 10. The improved storage wrap material of claim 1, wherein saidactive side when activated forms a releasable bond with a targetsurface.
 11. The improved storage wrap material of claim 1, wherein saidactive side includes a pressure sensitive adhesive.
 12. The improvedstorage wrap material of claim 1, wherein said sheet of materialcomprises a polymeric film material.
 13. The improved storage wrapmaterial of claim 12, wherein said polymeric film material issubstantially translucent.
 14. The improved storage wrap material ofclaim 1, wherein said active side comprises a plurality ofthree-dimensional non-adherent protrusions extending outwardly from saidsheet of material and a pressure-sensitive adhesive surrounding saidnon-adherent protrusions, said adhesive having a thickness less than theheight of said non-adherent protrusions before activation.
 15. Theimproved storage wrap material of claim 14, wherein said protrusions areunitarily formed from said sheet of material.
 16. The improved storagewrap material of claim 1, further comprising a dispenser, said sheet ofmaterial forming a continuous web wound to form a roll of storage wrapmaterial, said roll of storage wrap material being disposed within saiddispenser.
 17. The improved storage wrap material of claim 16, furthercomprising a core disposed within said dispenser, said sheet of materialbeing wound upon said core to form said roll of storage wrap material.18. The improved storage wrap material of claim 1, wherein saiddispenser comprises a carton.
 19. The improved storage wrap material ofclaim 1, wherein said dispenser includes a severing apparatus.
 20. Animproved storage wrap material comprising: (a) a sheet of non-poroussubstantially translucent polymeric film material having a first sideand a second side, said first side comprising an active side which isactivatible by an externally applied compressive force exerted in adirection substantially normal to said sheet of material, said activeside exhibiting an adhesion peel force after activation by a user whichis greater than an adhesion peel force exhibited prior to activation bya user and which is sufficient to form a continuous seal against atarget surface, wherein said active side comprises a plurality ofthree-dimensional non-adherent protrusions unitarily formed from andextending outwardly from said sheet of material and a pressure-sensitiveadhesive surrounding said non-adherent protrusions, said adhesive havinga thickness less than the height of said non-adherent protrusions beforeactivation, wherein a compressive force of at least about 0.1 psi isrequired to activate said active side, and wherein said sheet ofmaterial is linerless, such that activation of said active side requiresno removal of components of said sheet of material, said sheet ofmaterial being sufficiently flexible to conform readily to a desiredsurface and having sufficiently small resiliency that it does not exertundue restorative forces which would tend to cause said sheet ofmaterial to break contact with such a desired surface.